I am having the same problem as you are. Just picked up my 05 X5 over the weekend and the phone keeps rebooting everytime it try to load the phone book. I have read on other post where some people got their treo 650 to work but I cant seem to do that either.
Let me know what you find out.

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2011 X6 XDrive 50i/ Black Saphire/Oyster/Dark Wood/ Sport package/20" Alloy/Premium Package/Cold Weather/Rear Climate/Running Boards/Comfort Access/Rear View Cam